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  1. #1
    New Member
    Join Date
    Aug 2008

    Default B&S 13 HP Oil Breather Compartment Hole

    I have a John Deere GX85 Lawn Tractor. It is equipped with a B&S 13 HP Engine model number: 28M707, type: 1147-E1, code: 971017ZB. 2 valves, 1 cylinder.

    A brief history: Last season it was started without filling the crankcase with oil and it "died". I wasn't there but the report is that it just slowly died and didn't make a loud noise or jerk. My uncle took it to a witch doctor who charged me $35 to fix and said something about the carburetor needing to be cleaned. My uncle, God rest his soul, is no longer able to assist me in matters mechanical or otherwise so I don't know nor can find out what exactly went wrong when the engine overheated. I used it after that all season long. At the end of the season, I was running it out of gas and getting ready to winterize it when it died again. This time it made a bad noise--a semi loud clank to a more or less sudden halt. It being the end of the season, I just packed it away for storage and didn't get to it until this year (I have another mower that I have been using). Based on preliminary testing (the flywheel wouldn't rotated) was pretty sure I had thrown or rod or seized the engine. I removed the head and the piston pushed freely in with no damage to the cylinder wall so I assumed it was a rod. I acquired a manual and disassembled the engine to find that I had indeed broken a rod. I replaced it, the governor assembly/oil slinger (damaged), installed a new set of rings and fresh gaskets. And now...

    I buttoned it all back up and everything looks good--cylinder wall intact, valves straight and adjusted properly, etc. When I go to start it up it turns over a few times, sounds good, and then begins to backfire out of the air intake/filter. I checked the carburetor and it seems to be okay. I did a compression check by rotating the flywheel and letting it spin back into place and it didn't go back, or move at all. I then removed the oil breather cover and inspected the compartment as the drain hole may become clogged and cause this behavior or so says the manual. The drain hole is free of debris but I noticed that in the top right of the compartment there is a born hole 1/2" in diameter diagonally into the crankcase . It appears as though it was done with a drill bit.

    Is that born hole supposed to be there? Or is this perhaps the work of the mechanical witch doctor? Any advice on how to proceed?
    Last edited by Phredrick; 08-20-2008 at 04:07 PM. Reason: Wrong Image Link

  2. #2
    Veteran Member
    Join Date
    May 2005
    N. E. Florida

    Default Re: B&S 13 HP Oil Breather Compartment Hole

    Good chance you have a sheared flywheel key. That sudden stop will shear the key, much better than bending the crank. A sheared key changes the ignition timing because the magnet on the flywheel is in the wrong place.

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